module mux_2to1 (
    out, in0, in1, addr
);

    parameter n = 1;
    output reg [n-1:0] out;
    input [n-1:0] in0, in1;
    input addr;

    always @(*) begin
        case ( addr )
            0 : out = in0;
            1 : out = in1;
            default : out = 0;
        endcase
    end
        

endmodule